Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. In recognition of the potentially enormous expense of well completion, added emphasis has been placed on well monitoring and maintenance throughout the life of the well. That is, placing added emphasis on increasing the life and productivity of a given well may help ensure that the well provides a healthy return on the significant investment involved in its completion. Thus, over the years, well diagnostics and treatment have become more sophisticated and critical facets of managing well operations.
In certain circumstances, well diagnostics takes place on a near-continuous basis such as where pressure, temperature or other sensors are disposed downhole. For example, such sensors may be provided in conjunction with production tubing, laterally disposed frac-liners, chemical injection hardware, or a host of other completions equipment. That is, a monitoring tool with sensors may be affixed downhole with the equipment in order to track well conditions over time. In some cases, the monitoring tools may be fairly sophisticated with capacity to simultaneously track a host of well conditions in real-time. Thus, both sudden production profile changes and more gradual production changes over time may be accurately monitored. Such monitoring allows for informed interventions or other adjustments where appropriate.
In many cases, such called-for adjustments may involve minimal actuations such as the opening or closing of a valve, shifting the position of a sliding sleeve or other similarly low-powered maneuvers. As alluded to above, providing completions equipment outfitted with sensors may avoid the introduction of dramatically more costly logging operations. Thus, by the same token, efforts have been undertaken to outfit completions equipment with affixed tools suitable for achieving minimal actuations such as the noted shifting of a sliding sleeve. So, for example, the costly introduction of a separate coiled tubing intervention dedicated to sliding a sleeve may be avoided.
Providing continuous downhole power to completions equipment may face certain challenges. This is particularly the case where the completions equipment is installed throughout various lateral legs of a multi-lateral well, thereby rendering power supply via conventional electrical cable near impossible. For example, in order to supply a separate electrical cable to each lateral leg of a multi-lateral well, cabling may be dropped through a central bore. This results in separate cable lines exiting the bore into each separate lateral leg. Not only does this present significant installation challenges, the well is left with a myriad of cables running into and out of lateral legs and serving as impediments to follow on applications and/or production itself.
In order to avoid the challenges and obstacles presented as a result of power supply via electric cable, efforts have been made to direct actuation tools via hydraulics. So, for example, it may be possible to direct the shifting of a sliding sleeve in a lateral leg through the hydraulics of the well and/or completions equipment without the need to supply a dedicated electric cable to the vicinity of the sleeve. Of course, such efforts may be fairly sophisticated and lack a degree of reliability. Further, such efforts are impractical in terms of supplying power to monitoring tools. Thus, the effectiveness of the shifting of the sliding sleeve would remain unchecked by any associated nearby monitor.
Given the limitations on hydraulic power as noted above, more discrete and dedicated power supplies have been affixed to completions equipment in hopes of supplying necessary power for low-power monitoring and actuation. For example, completions equipment has been outfitted with lithium-based battery packages adjacent monitoring and/or actuation tools. Thus, in the case of a multi-lateral leg of the well, a monitor or actuation tool therein may be supplied with power directly from the associated battery pack.
The power requirements for the noted monitoring or actuations are small enough to be supplied by the indicated lithium-base batteries. Unfortunately, the life of such lithium-based or other conventionally available batteries is dramatically less than the life of the well. For example, in theory, such batteries may have a life ranging from about 2-3 years whereas the life of the well may be closer to 20 on average. Furthermore, in practice, as the batteries are employed and exposed to high temperature downhole conditions, battery life is even further reduced. As a result, operators may undertake repeated interventions for battery change-outs. Alternatively, repeated logging and actuation interventions may be undertaken with the option of discrete independently powered monitoring and actuation tools foregone altogether. Regardless the particular undertaking selected by the operator, the time and expense involved may be quite dramatic.